The air we breathe can contain dozens of toxins. The National Institute of Environmental Health Sciences (NIEHS) strategic plan for 2012-2017 includes a major focus on enhancing our ability to quantify individual exposures and responses to environmental toxins. Similarly, the US Environmental Protection Agency (EPA) is increasing its emphasis on community monitoring, so that citizens may better understand their exposures to toxins. However, equipping large numbers of individuals and/or geographic sites with available monitoring equipment capable of accurately measuring low levels of toxins would be prohibitively expensive. Therefore affordable devices capable of measuring personal exposures to toxic gases are urgently needed. Moreover, available simple toxic gas monitors have presented difficulties of operation and interpretation when deployed by lay personnel for community monitoring initiatives. Therefore personal exposure monitors must also be easy to use and interpret if personal monitoring is to be widely adopted. One air pollutant that is challenging to measure affordably at low levels with specificity and accuracy is formaldehyde (HCHO). This carcinogen is emitted from building materials among other sources, and can pollute homes and workplaces where the materials are installed or manufactured. Providing simple, affordable means of monitoring HCHO exposure would provide citizens with better, actionable information; epidemiologists with better data with which to assess health risks; and regulators with information needed to develop effective, defensible policies. Platypus Technologies has developed an approach to monitoring HCHO exposure that combines the company's proprietary liquid crystal (LC) sensing platform with a novel sensing mechanism. The platform is amenable to zero power readouts, and the sensors are inherently small and light weight, facilitating comfortable deployment on people. Platypus has commercialized the ClearSense(tm) hydrogen sulfide dosimeter based on LC technology for the industrial hygiene market, and now proposes to leverage this expertise for the more challenging task of HCHO detection. The LC sensing platform is uniquely amenable to a novel surface chemistry strategy for detecting HCHO that is designed to improve specificity over currently available sensors. The strategy involves fabricating a chemically reactive surface on which LCs align parallel to it. On exposure to HCHO, the LCs realign perpendicular to the surface. This realignment causes sensors to change from bright to dark when viewed through crossed polarizers. The long-term goal is a chemical dosimeter product for HCHO suitable for personal exposure monitoring. To minimize fabrication costs and improve performance for long-term monitoring, we propose to modify sensor design from the Clear Sense product concept by (i) supplanting the use of gold-on-glass sensor surfaces with saline- on-glass, to save costs and extend sensor stability; (ii) reducing sensor surface area, further reducing costs; and (iii) replacing the LCs traditionally used for sensors with LCs that have greater resilience to changes in temperature and moisture, an option not previously possible that is afforded by the novel detection chemistry.